"Where you need to be is in the air dropping bombs on your enemy. That is the support your family needs."

This is the advice that 1940s veterinary surgeon James Herriot (Nicholas Ralph) receives from his Royal Air Force commander FO Woodham (Sam Retford) on the Season 4 finale of "All Creatures Great and Small," which are based on the books by Alf Wight. James has requested temporary leave from training upon learning that his pregnant wife Helen (Rachel Shenton) may give birth soon. Oh yeah, and it's also Christmas. 

This year has been a test for James in ways he did not expect. The season began in spring 1940 with goat shenanigans and the demands of lambing, a typical time in the Yorkshire Dales for the denizens of Skeldale House. It was the period of what is referred to as the "Phoney War," the early months of World War II. 

"As the series continues, of course, the war starts to rumble on," Ralph said in an interview with Salon. "The Battle of Britain happens. And it's late summer into autumn, which is a massive point in World War II. And, of course, James has signed up to the RAF as well."

While James and his fellow Skeldale vet Tristan Farnon (Callum Woodhouse) had enlisted with the best intentions at the end of last season, James hadn't foreseen how married life would change his circumstances and mindset.

"They're in Skeldale, they've got their own little world, and they're about to start a family, at which point James gets called up," said Ralph. "And not only that, but a lot of men signing up and going off, you will know of men not returning, you'll know of men who have been killed in action. So the stakes are just so much bigger for James when he gets called up. It's a huge dilemma of heart and mind."

Nevertheless, James does his duty, which finds him training three counties over when he learns of Helen's precarious condition from a phone call and has his request for leave denied. Desperate to see his wife, James makes the surprising decision to go AWOL by stowing away in the back of a supply truck. Although he's caught and returned to base, once he fulfills a crucial duty, Woodham relents and allows James to visit home. That's when James learns that Helen has given birth and he gets to see his son for the first time. While he's overcome with emotion, he's also out of his element, not having dealt with human babies in his line of work. 

"There's a similarity to [the books] in the episode we filmed when he's holding little Jimmy," said Ralph. "He said, 'He's a funny looking thing, isn't it?' And then Helen says, 'Oh I suppose every foal that comes out is beautiful.' And that line is true to life. That's what James Herriot said for real, which I think was very funny.

"[In the books,] he talks about this smushed face, it's bright red, and some of the afterbirth still being there," Ralph continued. "He said, 'He looks like he's going through some inner turmoil," which is brilliant. He's at the midwife's house, and Helen's had the baby, and he actually asked to see another [baby]. He sees the one next door, looks down at this little baby and he thought, 'Oh, that's alright. Jimmy is fine because this one was even worse.'"

Check out the rest of the interview with Ralph who discusses driving vintage cars, brucellosis, working with birds of prey and ferret roulette.

The following has been lightly edited for length and clarity.

All Creatures Great and Small (PBS)James has this whole plan he's going to train this young vet who will help out in his absence. Could you discuss working with James Anthony-Rose who plays new vet Richard Carmody, and specifically what it's like to teach him to drive in that vintage car? Is it a functioning vehicle?

James thinks [Richard Carmody] is going to be a mini him and it's going to be brilliant. He'll take him under his wing, train him up. Turns out he's a mini Siegfried [Samuel West]. They end up getting on like a house on fire, and James kind of feels left at the side a little bit and becomes the kind the butt of the jokes. Richard Carmody, we see him flourish. He's very, very booksmart, but not so good on the practical side of things, at which point tending to  the horse that got loose, Siegfried and James come back together. Then you you see that they really need one another, which is lovely. 

Teaching James Anthony-Rose to drive was interesting because the actor himself doesn't drive. We had to have a stunt double in to do some of the driving and then the rest of the time was on a low loader. Those period cars are fully functioning. I drive them all the time. The little blue one is a Vauxhall, and the green one with the soft top is a Rover. The blue one, Sam always laughs about it, because it's the same age as his mum. It's roundabout 90 years old. There's obviously a lot of patchwork and upkeep. The interior, the seating, the dash, just everything is of the period. It's a lot of fun. I mean, the gearstick wobbles as much in gear as it does when you're in neutral. So you just throw it in a general direction and hope something sticks. The Rover on the other hand, very smooth to drive, lovely to drive. 

Do they go very fast? 

They do go a bit of a lick. You can get up to 40 miles per hour in that car where the wheels are six inches wide. It's a real workout driving that car.  There's obviously no power steering, and there are wooden padded brakes. But if you want to brake you have to brake 30 yards before the place you want to stop. You'd be better off braking like a Flintstone car, just digging your feet into the dirt. If you could, you probably stop quicker.

Something that came about with Richard Carmody is the the diagnosis for brucellosis. And that was a scary moment because of the concept of zoonosis where the disease can jump from one species to another. What did you learn about that? 

I wasn't aware of it beforehand. I mean, I knew about brucellosis because I did the audio books, so I'd come across that, but I didn't know that zoonosis part about it jumping from species to species. I was kind of learning it as James was learning it, which was really, really frightening very much so because vets could get brucellosis. 

In the books, James actually does catch brucellosis in the end. I think the final book – I just did the audiobooks – that was a brilliant chapter when he's almost delirious. He's in bed with a really high fever and he starts singing old Scottish tunes from home that are sung by these classical Scottish singers who are tenors. They've got these massive high bits, and he's like, "The high bits just came to me, and I was singing, and it's amazing." At this point, both the kids are born, Jimmy and Rosie, and they're at the door, just creasing themselves with laughter. James is in bed singing, obviously doing a terrible job, but to him and his delirium thinking it's just the most wonderful singing. There's a lot of fun to be had with that later on.

James does get called up. What sort of things did you learn about what it meant to enlist and get called up for the RAF? How far is he from home when he goes to training on the base?

He's three counties away. Yorkshire is the biggest county in the UK and England, so it's actually quite far away. We know that James ends up being called to the bombers, so I learned a lot about that. In about 51% of bomber crews, personnel didn't come back. So it's less than half, a less than 50% chance you would return. Another 25% were injured in training and in action. The odds against you coming back in one piece is high, staggeringly high. In the Lancaster bombers, those planes roughly managed about six missions on average before they were they were taken down. So it's really not great stats.

You'd be learning about that during training, you would be seeing men not coming back, as we had in the Christmas episode of the young man that James gets to know because like himself, he's got a young family, a couple of kids. That really is like a sledgehammer to the chest for James. I think when you're doing basic training, it's almost like you're miles away from being in on missions. And that reality really sinks in for him in that moment. Also during the Battle of Britain, they fast-tracked recruits through the process so you can be in the sky I think six months from arriving for basic training.

As a result of that, James goes AWOL and tries to get back to Darrowby by sneaking into the back of a truck. Was that you who hopped into the truck?

That was me. The first take I got in, and it was good. The second one, I got in but kind of slithered over it like a slug. And the third one was that one, which I thought was quite quite good. It's actually higher than it looks on screen. It was actually quite a leap to get up there with all that gear on, the four layers and the big trench coat and the big boots I had to wear. So I was actually I was chuffed about that. 

Can you take us inside James's head when he does go AWOL? Did a lot of trainees go AWOL or at least try like James did?

I don't think that many [tried] to be honest, especially at that point in training. Again, this is true to life. This is something that Alf Wight, James Herriot being his pen name, did. It's in the books. He had been AWOL twice actually: once just to see Helen, and then the second time when he knew roundabout the time that she was due to give birth.

It just speaks of the their bond and their connection. We had spoken about an hour with their [real-life] kids, Jim and Rosie. And they just talk about that bond; they were just an absolute team, James and Helen were. They didn't really argue, they always had each other's backs. it just speaks of that connection that they have because James is somebody who [usually] follows the rules. In the earlier seasons, he was trying to do his best trying to impress Siegfried, trying to keep his job. For James to decide to go AWOL, he could have ended up in military prison. In that moment, I think it's almost instinctual. I don't think thinking is really coming into it too much. It's impulsive. 

Why do you think the officer Woodham relented and even personally delivered James to Darrowby, especially after giving that big speech about keeping focused and hard-hearted?

I think he could probably see within James that burning desire. He's also managed to get the bird flying, which is good. And it is Christmas, and his wife is pregnant. So yeah, it's probably a combination of all those things, really. Maybe about the Christmas spirit as well.

All Creatures Great and Small (PBS)Speaking of the bird, James is instructed to use his skills as a vet to get the kestrel Georgie, flying again after she injured the feathers in her wing. What can you tell me about the role of these birds during wartime?

It's the mascot of the base there, one of those kind of slightly superstitious things, like you might wear the same pair of pants when you go up for a flight. I had my own things when I played football as well.  For the guys, it comes at a time when there has been a plane down the night before. The morale is kind of low. So just to have that mask on, have that bird fully fit and well and taking flight is a little good luck thing before before the missions. I think for the men it is really big. Yeah. So thankfully, James was able to help the bird out.

You've worked with so many animals on the show over four seasons, but the kestrel is new. What was it like working with and handling the bird? I'm not sure of the bird's real name but in the show it was called Georgie.

That was a bit of art imitating life that week in that I was away up in Elvington at the RAF Aerodrome museum. So everything is as it was during World War II. You're just completely transported back in time. It was amazing. And then especially when everyone was in the costumes, and you're surrounded by 30 extras, that was absolute incredible being there. Like James, I left the rest of the cast back in Harrogate and filming there. I was away for a week, so I did miss the miss them. 

So the day before we started filming out there, I spent just the afternoon with the animal handlers and Grace, the little kestrel. It was just incredible. I love birds of prey. I just think they're so majestic. She was just brilliant. We were doing little calls. For one of the shots, she had to hover at a certain spot. So you'd let her fly off and then you'd have food in a slingshot. And then you would call the bird and point above you to the spot that you want to do to hover at. You would do this call and point, call and point and then she would swoop down and hover at the point that you are pointing at, and then you fire up the food for her to catch. That's how they had her hover at that one point for one of the opening shots when she's hovering and then it turns into the biplane.

Are there any other tips that you learned about handling a bird of prey or kestrel?

Your arm has to be at a 90-degree angle, like this. And it should be on your hand, and you need a loose grip. Then you always have the bird looking into the wind because if you don't, she'll always try to maneuver to look into the wind. That's when they're ready, they're primed and then they'll set off. If you try to carry the bird with its back to the wind, it will actually fall off your hand and be upside down and flapping around. You always have to move yourself. So normally, you're walking backwards into the wind a lot of the time.

James fixes the kestrel's wing using a toothpick in the hollow shaft of the feather as a termporary measure. Would that actually work? Was that in the books? 

Now I have to be careful what I say here, but I don't recall it from the book. I am going through them quite thoroughly. I think that's one of the ones from our on-set vet Andy Barrett, who we consult with over scripts and things like that. Thankfully for us and for James in that scenario it worked.

All Creatures Great and Small (PBS)Right now, we're still waiting to hear if there will be a fifth season, which I don't doubt we'll hear about soon. In the meantime, can you reflect on how the show carries on the legacy of Alf Wight and his vision?

The books have been translated into 45 different languages and sold 50 million copies plus worldwide. This the reach is global. The show now is in every continent, and, and then lots and lots and lots of countries within those continents. It all comes down to the material because they're so steeped in truth and love, not only for the animals, but for one another. The characters and the relationships within are so three dimensional. There's so much truth to it, and people can relate to it. I think he's a real humanist, Alf Wight was.

That's why these books transcend time and place in the way that they do so, with the wonderful Yorkshire Dales and these fantastic characters. These eccentric characters still come across who still they still exist as well. We were working at a farm without with a farmer there and somebody said, "You know, if you picked him up and put him in the show, nobody would believe you." Because he was just this proper eccentric guy, a lovely guy. They're so quirky, some of the characters, and but they're still truthful.

Speaking of colorful characters who seem unbelievable, what can you tell me about the ferret roulette? Was that in Alf Wight's books?

That was something that was added, but it was brilliant fun and obviously researched from that period. It's another one of these kinds of pub games where the dealer always wins it seems. We did that for real as well. It was a real ferret. Also when when he got loose going across the square across Grassington, across Darrowby, we did that for real as well. That took a few attempts. One time he went over that way, the next time he went over over to his right and then finally he got going the right way.  Working with animals is a complete joy, even when you're working with those bigger, intimidating animals: the bulls, the horses and the cows. Working with them brings a whole new focus to the set. Everybody's really on their toes. There's a different kind of energy and a calmness and a focus.

Can you reflect on this ongoing gift that "All Creatures Great and Small" had been, especially during the time when a lot of people needed the show?

It's absolutely incredible. At the start of the year, we were out at the L.A. Zoo, doing a screening of the first episode, and we met some fans. That was the absolute highlight of the trip. It just so many people with just lovely things to say. And such a wide demographic as well, people that came down to say hi and get a picture. Lots of different stories about how it came at a certain time for them if somebody was maybe unwell or they were struggling personally. It's just the thing that gets the whole family together, and you'll have three generations sitting down and watching the same television show. That's something we're incredibly proud of.

We get messages all the time as well on social media. I did a video recently. A woman's daughter got in touch and told us about how her mum had terminal cancer, and she's a massive "All Creatures" fan. She's a massive fan of the books and everything and now a massive fan of this series. When they get together, the family, they put that on because it makes her smile. So I sent them a little video message.

It came out at a time when we were all stuck inside and we didn't know what was going on.So they'd have that kind of escape out to the Yorkshire Dales with these characters and this community in having the onus on your neighbor and this kind of gentle, warm drama with laughs. Since then, you know, we've had a wonderful time making four seasons and and we'd love to do more. It's is a real treat and continues to be.

Besides hopefully more "All Creatures," what's next for you?

A couple of jobs unfortunately were affected by the strikes, because they're both American-led things. But there will be some things coming out this year. It's a TV series, so look out for me in that. Then hopefully in the spring or the summer, I'll go on all these things that were pushed because of the strikes.